New items can be added to the invoice even when it is created. To add a new Item in the invoice, follow the path as decribed below
Business Profile > Sales > Sales Order New > Invoice Details > Add items
Go to List of Invoices
All the invoices of the selected filters will be opened to you
By following this process, you will be redirected to “Add Items” screen
Start typing the product name in the input provided and suggestions will start showing in the list below
Click on the item name and its details will be filled in the inputs provided
You can add multiple items at once if you wish to. Once completed, click on “Save” button to add selected items in an invoice.
Your items will be added in the invoice